| Cover | Dec. 16, 2023 |
| Cover [Abstract] | |
| Document Type | S-1 |
| Amendment Flag | false |
| Entity Registrant Name | PHIO PHARMACEUTICALS CORP. |
| Entity Central Index Key | 0001533040 |
| Entity Tax Identification Number | 45-3215903 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 257 Simarano Drive |
| Entity Address, Address Line Two | Suite 101 |
| Entity Address, City or Town | Marlborough |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01752 |
| City Area Code | (508) |
| Local Phone Number | 767-3861 |
| Entity Filer Category | Non-accelerated Filer |
| Entity Small Business | true |
| Entity Emerging Growth Company | false |
| Document Creation Date | Dec. 19, 2023 |
